1. Field of the Invention
The present invention relates to apparatus and process for plasmapheresis, and, more especially, to such apparatus/process employing a membrane separator.
2. Description of the Prior Art
Plasmapheresis is a known operation consisting of separating the whole blood of a donor into two fractions, the first fraction constituting the plasma phase and the second fraction constituting the cellular component phase, which is typically injected back into the donor. The plasma phase is a complex aqueous solution containing proteins in particular, while the cellular component phase, which still contains plasma, comprises the red corpuscles (or erythrocytes), the white corpuscles (or leucocytes) and the platelets.
The technique of plasmapheresis has long been used in animal experiments. Compare, for example, the article by John J. Abel et al entitled "Plasma Removal With Return Of Corpuscles" published at J. Pharmacol. Exp. Ther., No. 5, pages 625 to 641 (1914), in which dog's blood is centrifuged in order to perform the separation. There may also be mentioned the article by A. Geiger published in J. Phys., 71, pages 111-120 (1931) and entitled "Method Of Ultrafiltration In Vivo", which describes a continuous plasmapheresis operation on dogs, the separating apparatus employed being a membrane separator, and the membrane being arranged in a spiral and being selected such that it is possible, if desired, to obtain a plasmatic solution comprising the entirety of the proteins from the blood treated.
Plasmapheresis has also been applied to man for a certain number of years, as indicated by the article "La plasmapherese--Technique--Indications" ("Plasmapheresis--Technique--Indications") by Fr. Oberling et al, published at J. Med. Strasbourg, pages 277-279 (March, 1968). Thus, plasmapheresis now tends to replace the total donation of blood, because this technique has the advantage of enabling larger amounts of plasma to be withdrawn from a human donor without serious drawbacks. Because the formed elements of the blood are returned to the donor, the withdrawal sessions can be carried out at shorter intervals of time than for the donation of blood.
Thus, plasmapheresis is an old technique and the subsequent improvements which have been made thereto involve either improved centrifugation apparatus or improved membrane apparatus therefor. In the patent literature featuring improvements in membrane apparatus, reference is made to Amicon's German Patent No. 2,100,209 which describes a vessel comprising a membrane forming a spiral, for the circulation of whole blood withdrawn from a donor, and in which a pressure is exerted on the blood contained in the vessel, either by means of a gas or by means of the piston of a syringe, subjected to the action of a leaf spring. Compared with the apparatus of Geiger described above, this apparatus, by its very design, has the disadvantage of not permitting a continuous operation to be performed on the donor.
Also representative is Hemotherapy's U.S. Pat. No. 4,191,182 which describes membrane apparatus and in which blood continuously withdrawn from the donor is separated into plasma and into a cellular fraction continuously returned to the donor, such apparatus having the particular characteristic of allowing a portion of the cellular fraction to recirculate in the upstream compartment of the membrane apparatus and of allowing the plasma fraction to recirculate in the downstream compartment of the same apparatus. Cf. the International Application of Friedman et al published under International Publication No. WO 79/01121, which also deals with apparatus enabling the withdrawal of blood from the donor and injection back into the donor of the fraction which has not passed through the membrane, in a continuous operation.
However, the types of equipment described above, which permit continuous plasmapheresis, display the particular disadvantage of requiring the donor to be injected at two separate points, which is rather unpleasant for the donor.